A considerable body of patent literature exists over a period of many years relating to the electrodeposition of palladium metal. This prior art is represented by the following U.S. Patents:
U.S. Pat. No. 330,149--Pilet et al. PA1 U.S. Pat. No. 1,921,941--Powell et al. PA1 U.S. Pat. No. 1,993,623--Raper PA1 U.S. Pat. No. 2,207,358--Powell et al. PA1 U.S. Pat. No. 2,451,340--Jernstedt PA1 U.S. Pat. No. 3,150,065--Fatzer PA1 U.S. Pat. No. 3,206,382--Wilson PA1 U.S. Pat. No. 3,458,409--Hayashi PA1 U.S. Pat. No. 3,480,523--Tyrrell PA1 U.S. Pat. No. 3,530,050--Ickenham et al. PA1 U.S. Pat. No. 3,544,435--Angus et al. PA1 U.S. Pat. No. 3,580,820--Yamamura et al. PA1 U.S. Pat. No. 3,920,526--Caricchio PA1 U.S. Pat. No. 3,933,602--Henzi et al. PA1 U.S. Pat. No. 4,076,599--Caricchio, Jr. et al. PA1 U.S. Pat. No. 4,092,225--Davis PA1 U.S. Pat. No. 4,098,656--Deuber PA1 U.S. Pat. No. 4,144,141--Schuster et al. PA1 U.S. Pat. No. 4,297,177--Fletcher PA1 Palladous diamine chloride--Pd(NH.sub.3).sub.2 Cl.sub.2 PA1 Palladous diamine dinitrite--Pd(NH.sub.3).sub.2 (NO.sub.2).sub.2 PA1 Palladous tetramine nitrate--Pd(NH.sub.3).sub.4 (NO.sub.3).sub.2 PA1 Palladous diamine sulfate--Pd(NH.sub.3).sub.2 SO.sub.4
The problems usually encountered in the known palladium metal electroplating baths, including limited deposition rates and brittleness due to hydrogen embrittlement were set forth in several papers presented at The Second AES Symposium on Economic Use of And Substitution For Precious Metals in The Electronics Industry held on Oct. 5th and 6th, 1982 at Danvers, Mass. The papers were by J. A. Abys "A Unique Palladium Electrochemistry Characteristics and Film Properties" and by H. S. Trop and A. V. Siaweleski "Application of BTL Pd Technology to Barrel Plating."
It is apparent therefore that there is a need for commercial palladium metal baths which will efficiently operate at high speeds over a wide range of current densities to produce a ductile palladium deposit on a variety of substrates.